= Surface area of a tricylinder
{title2=$A=24a^2(2-\sqrt2)$}
For three radius-$a$ <circular cylinders> with mutually perpendicular axes through one point, the <boundary> of their common intersection has three congruent <cylindrical surface> pieces. On $x^2+y^2=a^2$, the height restriction is $|z|\leq a\min(|\sin\theta|,|\cos\theta|)$. Eight congruent sectors give <surface area> $8a^2(2-\sqrt2)$ per piece. Pairwise intersections are <curves> of zero <surface area>, so the three pieces add.
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